= Joseph Wu
{disambiguate=electrical engineer}
{c}
\b[Joseph Wu] is the named author of Texas Instruments' 2018 guide to <resistance thermometer> measurements, revised in 2023. The guide connects sensor wiring, excitation <electric current>, <reference resistors> and <analog-to-digital converters> rather than treating the converter as a complete thermometer by itself.<A Basic Guide to RTD Measurements by Joseph Wu>[Title page, revision record and §2, measurement circuits]{ref}
One concrete design distinction is between <two-wire resistance measurement> and <four-terminal sensing>. In the two-wire arrangement, the same leads carry excitation <electric current> and contribute to the measured <electric potential difference>. Their <electrical resistance> is therefore counted with the sensor. Separate sense leads with high <input impedance> can exclude that series drop, although input leakage and other nonidealities still require attention.<A Basic Guide to RTD Measurements by Joseph Wu>[§2.1.3, lead-wire error; §2.6, four-wire measurement]{ref}
For an original ideal example, let a sensor have <electrical resistance> $R_T=100\,\Omega$, with two $1\,\Omega$ leads carrying $I=1\,\mathrm{mA}$. <Two-wire resistance measurement> gives
$$
V=I(R_T+R_{L1}+R_{L2})=102\,\mathrm{mV},\qquad \widehat R_T=V/I=102\,\Omega.
$$
The \b[$2\,\Omega$ lead error] remains even when a shared <reference resistor> cancels excitation variations in the <ratiometric measurement>. Ideal <four-terminal sensing> instead measures $IR_T=100\,\mathrm{mV}$ directly across the sensor. This illustrates the <platinum resistance thermometer lead resistance error> mechanism without assuming a particular resistance-to-temperature calibration.
A proposed bench comparison replaces the sensor with a stable calibrated <resistor> and adds known series <resistors> to its current leads. Comparing two-wire and <four-terminal sensing> readings then tests lead-drop rejection without changing sensor temperature. The calculation distinguishes the wiring error from <sensor self-heating in a ratiometric resistance measurement>, which changes the sensor's actual <electrical resistance>.
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